Each year Thomson Scientific (formerly
the Institute for Scientific Information) publishes an update of its Journal
Citation Reports, which summarize the ways authors of journal articles cite
other articles.The statistic of most
interest is the journal impact factor, which is the number of times per year
the average article in a given journal in recent years (2002, 2003) was cited
in all journal articles in the previous year (2004).Impact factors provide only a rough measure
of quality of articles in the various journals.For more information and a critique, read
the article
that accompanied last year's list at this site. The journal Nature, which
enjoys one of the highest factors (currently 32), also featured an editorial
in June that was critical of "the unhealthy reliance on impact factors
by administrators and researchers’ employers worldwide to assess the
scientific quality of nations and institutions, and often even to judge
individuals".

This year Thomson Scientific insisted
that I provide a shorter list of journals and approximate values for some
journals, to comply with its policy of acceptable use.I have therefore focused on the core
journals of sport and exercise science. I have also had to stop tabulating
factors for previous years in this article and to remove tabulations from
previous articles.You can access complete
citation data at Thomson Scientific's Web of Knowledge, if your institution has a subscription.

In my report for impact factors in 2003, I
noted that the typical change in the impact factor between years was
~±0.3.Assuming a change greater than
0.3 is therefore atypical or noteworthy, the following core journals showed
noteworthy increases since last year:Acta Physiologica Scandinavica (1.7®2.1), Journal of Rehabilitation Medicine (1.1®1.6), Leisure Sciences
(0.7®1.3), Pediatric Exercise Science (0.8®1.4), Physical Therapy
(1.6®2.0),
and Sports Medicine (2.4®2.8).The biggest winner is the Scandinavian
Journal of Medicine and Science in Sports, up from 0.9 to 1.7.Exercise
and Sport Sciences Reviews made a respectable entry on 2.3, after the
requisite three years since its first appearance as a journal.Two core journals showed a noteworthy
decline of more than 0.3:Clinical Journal of Sport Medicine
(1.8®1.4)
and Journal of Sports Sciences (1.3®0.9).

I doubt whether the changes in specific
journals reflect changes in quality of the articles therein.More likely, the changes are due either to
sampling variation, or to changes in the area of specialization of the
journal, or to changes in research activity in the journal's discipline.It worries me that a fall in a journal's
impact could result in a vicous cycle of decline, because some researchers
may save their best work for journals that are on the way up.My continuing to publish these factors
from year to year might help set such a vicious cycle in motion. Publishing this article is also inconsistent
with my critical view of impact factors, but my motives are partly selfish:the article is easy to write, it is
popular, and it may serve as a magnet to attract readers to the other
articles.

In the table below, "<1.0"
implies a value between 0.1 and 1.0.Journals without an impact factor are not in ISI's science or social
sciences databases, either because the journal is too new or the factor is
too low.